This invention relates to drive means and has particular, but not exclusive, reference to agricultural machines such as drives to straw choppers on combine harvesters, for example.
In agricultural machines, much use is made of flexible drive transmissions, which normally employ either chains or belts, and there always arises the problem of maintaining tension in the flexible member in order to preserve the integrity of the drive. Tensioning means are necessary automatically to compensate for any wear and natural stretching of belts which would otherwise give rise to possible belt slip and hence loss of drive, or for any wear in the links of chains which results in effect in "stretching" of the chain with the runs thereof becoming slack to the extent that the chain can jump off the drive sprocket and/or driven sprocket.
Typically, spring loaded tension pulleys (in the case of belts) or tension sprockets (in the case of chains) are employed as the tensioning means but these are not always convenient in that they take up room within the actual transmission and in certain circumstances, such as the use of a crossed belt to effect drive reversal, a tension pulley is difficult, if not impossible to employ. Problems also arise in providing satisfactory tension in relative long flexible drive transmissions from the standpoint of cost and maintenance.
The invention will be described primarily in the context of combine harvesters and it should be noted that the terms "grain", "straw", and "tailings" are used principally throughout this specification for convenience. It should be understood, however, that these terms are not intended to be limiting. Thus "grain" refers to that part of the crop which is threshed and separated from the discardable part of the crop material which is referred to as "straw". Incompletely threshed ears are referred to as "tailings".